Production of anethole from sulfate



United States Patent 3,038,945 PRODUCTION OF ANETHOLE FROM SULFATE TURPENTINE RESIDUES Murray Garber, Norwalk, Conn., and Richard Herrlinger, Hans Albrecht, and Leo F. Ciesielslsi, Panama City, Fla., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Sept. 9, 1958, Ser. No. 759,856 7 Claims. (Cl. 260-612) This invention relates to the recovery of by-products from the distillation residues of crude sulfate turpentine and more particularly to the production of anethole of commercially acceptable purity and odor from this source.

Refined sulfate turpentine and other pinene-containing products are obtained on a large commercial scale by distilling the crude sulfate turpentine evolved during the di gestion of southern pine wood by the Kraft process in which a cooking liquor containing sodium hydroxide and sodium sulfide is used. Although the residues from this distillation are known to contain higher boiling terpenes of potential commercial value they are so heavily contaminated with mercaptans and other malodorous organic sulfur compounds that they are usually burned as fuel. It is a principal object of our present invention to provide methods for producing a purified and deodorized anethole from these distillation residues while simultaneously recovering higher boiling terpenes therefrom. A further and more specific object is the provision of a method for removing from the anethole-containing fractions obtained from crude sulfate turpentine a type of impurity that is not encountered in anethole from other sources. Still further objects of the invention Will become appar ent from the following description when taken with the appended claims.

In carrying out the process of our invention We first separate from the residue which remains after vaporizing pinenes from crude sulfate turpentine afraction containing dipentene, pine oil constituents and anethole together with minor amounts of other high boiling residues. This fraction is preferably separated by steam distillation either at atmospheric pressures or at reduced pressures on the order of about 100 mm. of mercury absolute. The fraction so obtained is treated with an aqueuos hypochlorite solution to oxidize and remove malodorous organic sulfur compounds and is then further fractionated to separate the anethole from the dipentene and pine oil. The anethole is further purified by Washing with aqueous hypochlorite solution and is then redistilled. The distillate may be further purified by agitation with an aqueous caustic solution and redistillation, whereupon a good grade of anethole is obtained which can be used for purposes where complete freedom from undesirable odor undertones is. not required.

Separation of the anethole from the dipentene and pine oil can be accomplished by vacuum fractionation of the initial distillate in a fractionating column using reflux ratios on the order of about 7:1 or higher. This procedure permits the separate recovery of a dipentene fraction and a pine oil fraction which, after further purification, are of commercial grade. The pine oil fraction can be deodorized to the necessary extent by repeated washings with a 25% aqueous solution of sodium hydroxide or other alkali followed by washing with water. The bad odor of the dipentene fraction can be greatly improved by repeated washings with dilute aqueous hypochlorite solution.

Anethole produced by this distillation procedure sometimes contains decomposition products of the higher boiling terpenes which remain in the still. Anethole of better purity and higher freezing point can be obtained by removing only the dipentene and pine oil in the vacuum distillation, leaving the anethole in the still residue. This residue is then distilled with steam and the distillate is further fractionated to produce a high grade anethole. A product having a considerably better odor than that from the one-step fractionation process and a freezing point of 20 C. or higher can be produced by treating the steam distillate with aqueous hypochlorite solution and then fractionating it at a reduced pressure and with reflux ratios of about 7:1 and higher.

The above-described procedures produce a commercially acceptable dipentene solvent and a pine oil which has the alcohol content and physical constants of ASTM grade I pine oil. Although these products, as well as the anethole, are practically free from sulfur-containing impurities they still retain a slightly disagreeable odor. This is not particularly objectionable in the dipentene and pine oil products, but it tends to exclude the anethole from use as a flavoring agent and also to some extent in. soap and perfumes. We have found that the chief cause of the residual bad odor in these fractions is the presence therein of small quantities of amines which, in their free state, have a very strong and pungent odor. We found, how ever, that by removing these amine impurities we could obtain a marked improvement in the odor of the fractions.

Products of improved odor are obtained when the amine-containing impurities are removed at any convenient stage of the purification and separation process. They are preferably removed either from the first distillate from the crude sulfate turpentine distillation residues, which distillate contains the dipentene, pine oil and anethole fractions described above, or from any one of these fractions after it has been separated from the others. The amine impurities are separated by contacting the fraction with an acid or an acid-reacting substance such as the free acid form of a cation exchange resin, thereby converting the amines into their salts, and then separating the amine salts from the fraction. Our preferred method consists in agitating the amine-containing fraction with an aqueous acid such as sulfuric acid, hydrochloric acid, phosphoric acid or strong organic acids such as formic, acetic and oxalic acid. These acids are preferably dissolved in water to an 0.5-3% solution and the acidified Water is mixed with the amine-containing material. Upon standing the mixture separates into layers and the water layer containing the amine salt is drawn off and discarded. This procedure may be repeated several times, using about 5-25% of the aqueous acid solution on the weight of the arnine-containing organic material, although a smaller number of extractions with larger quantities of acidified water could of course be used. The extraction temperature may range from room temperature to about C.

The amine-containing impurities can also be removed by treating the fractions with a cation exchange resin such as those sold commercially as Dowex 50 or Arnberlite 120. These are sulfonated polystyrenes or polystyrene sulfonic acids which are washed with an aqueous acid such as hydrochloric acid and then with water, dried, and packed into a column through which the amine-containing fraction is percolated. It will be understood that other comparable procedures for converting the aminecontaining impurities into their salts and separating these salts from the fractions may be employed within the broad scope of our invention.

After the anethole-containing fractions have been contacted with an acidifying agent for the amine contained therein they are preferably Washed with water followed by an aqueous alkali such as a 15% sodium hydroxide solution. This treatment neutralizes any residual acid and also improves the color of the product. The treated materials may then be again agitated with an aqueous hypochlorite solution to complete the removal of sulfur compounds, if necessary, and subjected to additional fractionations.

The following experiment shows that the source of the persistent odor in anethole obtained from sulfate turpentine residues is the amine impurities. Turpentine still residue was further distilled with steam until approximately 75% of its weight had been volatilized. A sample of the distillate weighing 2.77 kg. was extracted five times by agitating it with 200 ml. portions of 1% aqueous sulfuric acid at 60 C. for 30 minutes. The combined acid extracts were made alkaline by adding sodium hydroxide solution and were then extracted with diethyl ether. The ether extract was acidified with hydrochloric acid, the ether was removed by evaporation and the resulting amine hydrochloride was dried under a vacuum. The yield was 1 gram, or approximately 300 parts per million on the original steam distillate, of a yellow waxy solid having only a faint odor. When this amine salt was made alkaline with sodium hydroxide the free amine had an extremely strong and pungent odor. Infra-red analysis confirmed the presence of amine in this product.

It will thus be seen that our invention makes available to industry a new and relatively inexpensive source of anethole and provides methods whereby this material can be recovered as a product of commercially acceptable ptu'ity and odor from still residues that have heretofore been regarded as an industrial waste. We believe that the presence of anethole in crude sulfate turpentine distillation residues is the result of isomerization of the methyl chavicol content of the pine wood by the alkali present in the digestion liquors, but our invention of course is not limited to any theory of the mechanism by which this material was formed. On the contrary, our invention is based on a recognition of the presence of substantial quantities of anethole in these distillation residues and the provision of methods whereby it can be recovered therefrom in a purified and deodorized and commercially useful condition.

In the present specification and claims We have referred to aqueous hypochlorite solutions as suitable deodoriz-ing and desulfurizing agents for use in our process. It will be understood that any Water-soluble alkaline inorganic hypochlorite such as the hypochlorites of sodium, potassium, calcium or magnesium may be used. We prefer to employ sodium hypochlorite because it is easily prepared from cheap and readily available chemicals.

The processes of our invention are further described and illustrated by the following specific examples. It will be understood, however, that our invention in its broader aspects is not limited to these examples and that modifications and substitutions of equivalent materials and operating steps may be resorted to within the scope of the appended claims.

Example 1 A 375 pound batch of turpentine still residue, obtained as still bottoms in the refining of sulfate turpentine, was washed with warm water to remove water soluble impurities and then subjected to a steam distillation at atmospheric pressure to a temperature of 180 C. to yield 268 pounds of a distillate. This was treated four times with a dilute (about 0.11%) aqueous sodium hypochlorite solution at 60 C. followed by washing with Water and dehydration at l20-l40 C. The washed and dehydrated distillate, weighing 262 pounds, was then separated into three fractions in a 5 ft. by 4 inch packed column under an absolute pressure of 87 mm. of mercury using a reflux ratio of :1. These were a dipentene fraction boiling up to 120 C. and weighing 68 pounds; a pine oil fraction weighing 87 pounds and boiling between 130.5 and 149 C.; and 40.5 pounds of an anethole fraction boiling at 161 C.

The pine oil fraction was treated several times with a 25% aqueous solution of sodium hydroxide followed by washing with water. This yielded a product meeting A.S.T.M. specifications for Grade I pine oil as to alcohol content and physical contents but the odor was only fair.

The bad odor of the dipentene solvent fraction was improved by repeated washings with dilute aqueous sodium: hypochlorite solution.

The anethole fraction was washed four times by agitation with 1% aqueous sodium hypochlorite solution and was then steam distilled. The distillate was agitated with about l015% of its weight of a 20% Sodium hydroxide solution and was then redistilled at 17 18 mm. Hg at a temperature of 119121 C. The product had a freezing point of 18.4 C., a refractive index at 25 C. of 1.5551 and a specific gravity at 15.5/15.5 C. of 0.988. This indicated a good grade of technical anethole. Its odor was acceptable for some uses but still had some undesirable undertones.

Example 2 The procedure of Example 1 was modified by first removing the dipentene and pine oil from the anethole by fractional distillation and then separating the anethole by steam distillation from higher boiling terpenes and other residues which tend to decompose during a final fractionation.

A 2658 gram portion of crude sulfate turpentine still residue was first washed with hot water and treated four times with an 0.24% aqueous sodium hypochlorite solution followed by washing again with water. It was then steam distilled under mm. of mercury pressure until a temperature of C. was reached and 1985 grams of distillate were recovered. This was first agitated with aqueous 0.4% sodium hydroxide solution, then with 0.24% sodium hypochlorite solution and then with water and finally dehydrated, A sample of the treated distillate, weighing 1855 grams, was then stripped of dipentene and most of its pine oil content by distillation in a 5 ft. by 1 inch packed column at 100 mm. mercury pressure, by removing 1028 grams of a cut boiling from 98 C. to 150.5 C.

The distillation residue, which weighed 827 grams, was then steam distilled at 100 mm. 'of mercury pressure to yield 623 grams of a distillate consisting of anethole containing some of the remaining pine oil. This was agitated with a 0.24% sodium hypochlorite solution and then dehydrated and fractionated at 50 mm. of mercury pressure and a 10:1 reflux ratio in the column described above; There was obtained 300 grams of anethole which analyzed 96.8% pure by ultraviolet spectrophotometric analy-. sis and had a freezing point of 204 C. It was comparable to commercial rade anethole from other sources but it was not suitable for refining into NF grade anethole because of its odor undertone.

The overall yields from this process were 350 grams of a dipentene solvent and 850 grams of pine oil of commercially acceptable grade together with' the 300 grams of anethole.

Example 3 A sample of sulfate turpentine still residue was first washed with water and then three times with an 0.24% aqueous solution of sodium hypochlorite with intervening water washes. The treated and finally washed residue was then steam distilled at 100 mm. of mercury pressur to yield 74.7% of a distillate This was extracted three times by washing with 10% by volume of a 1% aqueous sulfuric acid solution at 30 C. for 0.5 hour and then washed with water. Following the acid treatment the distillate was washed three times with 20% by volume of an 0.24% sodium hypochlorite solution containing 2% excess NaOl-I for 0.5 hour at 60 C.; it was then washed with hot water and dehydrated at 100 mm. of mercury pressure by heating at 90100 C. v

The treated and dried distillate was then fractionated in a packed column at 100 mm, of mercury pressure and using a reflux ratio of 10:1 in order to remove the dipentene and pine oil fractions boiling between 98 C. and 150 C. The still residue, which contained the anethole, was then steam distilled at 100 mm. of mercury pressure to obtain a 78% distillate based on the still charge. This distillate was washed three times with aqueous sodium hypochlorite solution and with wate and was then refractionated at 50 mm. pressure to remove an additional fraction boiling between 131 C. and 144.5 C. and to produce an anethole of technical grade boiling at l44.5 C.

Example 4 A sample of the same sulfate turpentine still residue used in Example 3 was treated and fractionated by exactly the same procedure except that the sulfuric acid wash was omitted. The results of the two examples were then compared, and were as follows:

Boiling Range Example 3 Example 4 C. mm. Hg Yield Odor Yield Odor Dipcntene 98420 100 23.2 Good. 22.8 Bad.

Fraction.

Pine OilFrac- 132-160 100 31.6 do 27.9 Do.

tion.

Anethole, 144.5 50 10.9 do- 10.7 Poor.

Technical Grade.

Ancthole Properties:

Congealing Point, C 19. 8 20. 4 Refractive Index, 25 O- 1. 5565 1. 5570 Specific Gravity, 15.5/15.5 0.985 0. 985

These results show that the acid washing step does not impair the percent yield or modify substantially the chemical analysis of the fractions but that it results in products having a satisfactory odor, eliminating the necessity of further purification.

Example A portion of the anethole product of Example 3 was refractionated in a 3 ft. by 1 inch Stedman column at a reflux ratio of 10:1 and a pressure of 50 mm. of mercury. The product boiling at 144.5 C. was an NF grade anethole having the following characteristics:

Congealing point, C 21.1 Refractive Index, 25 C 1.5585 Specific gravity, 25 C 0.983 Anethole, percent 99.0 Odor Excellent 2. A method according to claim 1 in which the anethole-containing fraction is contacted with acid by washing it with acidified water.

3. A method according to claim 1 in which the anethole-containing fraction is contacted with acid by percolating it through a bed of the free acid form of a cation-exchange resin.

4. A method of producing anethole which comprises steam distilling the residue remaining after vaporizing pinenes from crude sulfate turpentine and recovering a distillate containing dipentene, pine oil and anethole, Washing said distillate with aqueous alkaline inorganic hypochlorite solution and separating the anethole from the dipentene and pine oil by distillation, and purifying the anethole by washing it with aqueous hypochlorite solution and redistillatio-n.

5. A method of producing anethole which comprises steam distilling the residue remaining after vaporizing pinenes from crude sulfate turpentine and recovering a distillate containing dipentene, pine oil and anethole, washing said distillate with aqueous alkaline inorganic hypochlorite solution and separating the antehole from the dipentene and pine oil by distillation, and purifying the anethole by washing it with aqueous hypochlorite solution and distilling it with steam.

6. A method of producing anethole which comprises steam distilling the residue remaining after vaporizing pinenes from crude sulfate turpentine and recovering a distillate containing dipentene, pine oil and anethole, washing said distillate with aqueous alkaline inorganic hypochlorite solution and then distilling dipentene and pine oil therefrom, separating anethole from the residue by distilling it with steam, and purifying the separated anethole by washing it with aqueous hypochlorite solution and again distilling it with steam.

7. A method of producing anethole from the residue remaining after vaporizing pinenes from crude sulfate turpentine which comprises distilling from said residue a fraction containing dipentene, pine oil and anethole, converting the small quantities of amines in said fraction into amine salts by contacting it with an acid, washing said fraction with water followed by aqueous alkaline inorganic hypochlorite solution and separating the anethole from the dipentene and pine oil by distillation, and purifying the anethole by washing it with aqueous hypochlorite solution and distillation.

References Cited in the file of this patent UNITED STATES PATENTS 1,777,704 Smith Oct. 7, 1930 1,928,020 Humphrey Sept. 26, 1933 1,977,064 Humphrey Oct. 16, 1934 2,243,802 Hasselstrom et al. May 27, 1941 OTHER REFERENCES Wagner: Manufactwring Chemist, vol. 23 (1952), pages 56-59. 

1. A METHOD OF PURIFYING AN ANETHOLE-CONTAINING FRACTION OF THE RESIDUE REMAINING AFTER VAPORIZING PINENES FROM CRUDE SULFATE TURPENTINE WHICH COMPRISES CONTACTING SAID FRACTION WITH AN ACID AND THEREBY CONVERTING THE SMALL QUANTITIES OF AMINES THEREIN INTO AMINE SALTS AND THEN SEPARATING SAID AMINE SALTS FROM SAID FRACTION. 